Cinematographic apparatus



Dec. 15, 1931:. E. DEH'MICHEN 1,836,613

CINEMATOGRAPHIC APPARATUS Original Filed 001;. 5,, 3.927

Patented Dec. 15, 1931 PATENT OFFICE ETIENNE OEH'MIGHEN, OF VALENTIGNEY, FRANCE CINEMAT'OGBAPHIG APPARATUS Original application filed October 3, 1927, Serial No. 223,822, and in France January 15, 1927. Divided and this application filed December 4, 1928. Serial No. 323,660.

The present invention relates to improvements in cinematographic apparatus comprising means for drawing the film by successive movements through the gate, and feeding sprockets disposed at the entrance and the outlet of the gate and adapted for continuous rotation. The invention chiefly relates to apparatus of this class specified in the patent application in my name, now pending, Ser. No. 223,822, filed Oct. 3, 1927, of which the present applicationis a division and in which the film rubs upon friction members situated between the reels andthe said sprocket respectively, in order to automatically reduce the tensions of the film periodically produced by the variations of the driving torque, variations of inertia, of friction and the like, thus reducing the wear and stress of the film.

In apparatus of this class of the known types, the film rubs directly on the friction parts situated between the reels and the respective feeding sprockets, but herein, due to the elasticity of the film, the tension is not produced in an absolutely instantaneous man ner, and when the film is braked there may be produced between the film and the friction surfaces a very slight slip whereby the film may be streaked.

It is feasible, while obtaining practically the same advantages as with the said apparatus, to revent all slipping of the film upon the friction surfaces and hence to entirely eliminate this cause of streaking.

In the accompanying drawings:

Fig. 1 shows one form of the invention.

Fig. 2 is a perspective view of another form of construction.

Fig. 3 is a view in elevation of a third form.

As shown in Fig. 1, the film travels upon a guiding drum disposed between the winding reel a and the feeding sprocket 72 disposed at the outlet of the gate, said guiding drum consisting of a cylinder of a substance whose coeflicient of friction is great relatively to the film this latter being guided by the lateral checks 2.

The shaft 3 of the guiding drum 1 is rotatable in supports 4 which are sup orted by elastic means 5 or by the action of counterweights (not shown) by which the weight of the drum will be balanced. At a short distance from the guiding drum is disposed a rotatable, and the tensions T and t on the.

film before and after traveling on the drum 1 are practically equal.

If the tension T of the reel tends to increase, the downward efi'ort F on the drum 1 will increase, so that the drum, overcoming the resistance of the elastic means or the counterweight, descends and makes contact with the brake shoe, thus at once reducing the tension t, so that the stress on the film when in contact with the stepwise film-drawing device will be reduced, in the known manner.

If the couple produced by the friction of the brake shoe on the drum 1 exceeds the couple exercised on the said drum by the moving film, the drum will be held against rotation by the shoe, and the film will thus slide upon it, and the film may thus be scratched.

According to the present invention, this risk is avoided, since the nature and the radius of the friction surfaces of the drum and the shoe are such that the friction couple of the film on the drum will exceed the friction couple of the shoe on said drum, and thus when the drum makes contact with the shoe, said drum will slip upon the shoe, and all slipping of the film on the drum is obviated.

In the form of construction given by way of example in Fig. 2, 7 is a drum which may be faced on the periphery by a layer 8 of a substance having a great coefiicient of adhesion relatively to the film. The shaft 9 of said drum is mounted in the bearings 10 movable on the guides 11 and supported by the springs 12, and it carries a wheel 13 of smaller diameter than the said drum and whose periphery, under the efiort F overcoming the resistance of the springs 12, may make contact with a brake member 14 slidable in supports 15 and controlled by a spring 16. The film is guided by loose rollers 17, and it travels in the direction of the arrow 2.

Due to the difference in the diameters of the drum 7 and the wheel 13, it is easy to obtain conditions such that the friction couple produced by the shoe 14 will always be less than the couple produecd by the film, so that the film will not slip on the drum.

Fig. 3 shows a modified form of the said device, in which the guiding and braking drum consists of a series of disks of a very adhesive substance 18 alternating with disks of a substance which is generally less adhesive 19 and of smaller diameter. The shaft 20 of the drum is mounted in the bearings 21 adapted to slide upon the guiding members 22. The bearings 21 are controlled by the reaction springs 23 which may be properly adjusted, so that the least effort of tension of the film will bring the parts 19 of the drum into contact with the brake shoes 24 which are stationary or are mounted on spring strips. The film 25 is wound on the lower part of the drum, and then travels upon the flanged guiding rollers 26 which are symmetrically disposed with reference to the plane of the figure. .The operation is the same as before.

Claims 1. In a cinematographic apparatus, the combination of a rotatable guiding drum having a shaft therethrough upon which the film travels and is in contact while forming a loop, slidable supports for the shaft of the said drum, springs supporting said supports, a brake wheel secured to said drum, a brake shoe situated at a short distance from said brake wheel and on the side opposite the loop, said spring supports allowing the drum to move under the pressure of the film in such manner that the said wheel will make contact with the said brake shoe.

2. In a cinematographic apparatus, the combination of a rotatable guiding drum having a shaft therethrough upon which the film travels and is in contact while forming a loop,

slidable supports for the shaft of the said drum, springs supporting said supports, a brake wheel secured to said drum, a brake shoe situated at a short distance from said brake wheel and on the side opposite the loop, said spring supports allowing the drum to move under the pressure of the film in such manner that the said wheel will make contact with the said brake shoe, said wheel having a diameter smaller than that of the said drum.

3. In a cinematographic apparatus, the combination of a rotatable guiding drum havin trunnions on which the film travels and is in contact while forming a loop, slidable supports for the trunnions of the said drum,

springs supporting said supports, a brake wheel secured to said drum, a movable brake shoe situated at a short distance from said brake wheel and on the side opposite the loop, said spring supports allowing the drum to move under the pressure of the film, in such manner that the said wheel will make contact with the said brake shoe, a guiding rod disposed on said shoe, a guide in which said rod is slidable, an a spring acting in opposition to the sliding of said rod when the said brake drum makes contact with the said shoe.

4. In a cinematographic apparatus, the combination of a rotary drum upon which the film travels and is in contact while forming a loop, braking means carried by the said drum, a brake shoe laced at a short distance from the said bra ing means for the said drum and on the side opposite the loop, movable supports on which the said drum rotates and adapted to allow the said drum to move under the action of the pressure exerted thereon by the film and to permit the said braking means to make contact with the said brake shoe, the size and material of the said brake shoe being chosen so as to exercise upon the said drum a couple of braking less than the couple exercised by the film on said drum, for the purpose specified.

In testimony whereof I have hereunto affixed my signature.

ETIENNE OEHMICHEN. 

